Drag Reduction Applications Research Articles

Functionalized super-hydrophobic nanocomposite surface integrating with anti-icing and drag reduction properties

Anti-icing and drag reduction are two significant issues for aircraft, but functional surfaces integrating both properties are rarely reported. Here, we propose a functional super-hydrophobic nanocomposite surface with sharkskin-like groove structures, which achieves the combination of anti-icing and drag reduction properties. The nanocomposite surface was prepared by stripping polydimethylsiloxane doped with carbon nanotubes from a laser-prepared sharkskin-like structure mold and then spraying a layer of polytetrafluoroethylene hydrophobic coating. The microstructures and nanoparticles with low surface energy provide the surface with hydrophobicity and icephobicity, enabling droplet transitions between Cassie and Wenzel states during icing-melting process. Carbon nanotubes enhance the Joule heating performance when voltage is applied. Ice at interface melts into water film, significantly reducing adhesion and enabling efficient anti-icing. Under the influence of the bionic sharkskin riblet structure, the vortices are lifted and pinned above the riblet tips, which reduces the near-wall velocity gradient and total wall shear stress, ultimately leading to lower drag. In addition, the flexible surface undergoes adaptive deformation to more effectively conform to the fluid flow during motion. The riblet protrusions increase the contact area between the flexible surface and the fluid, thereby enabling the absorption of more turbulent energy and fluctuations, further reduces drag. This study presents a new method for manufacturing functional surfaces for practical anti-icing and drag reduction applications.

Lotus leaf and shark skin-inspired micro-, nano-, hierarchical superhydrophobic surfaces for anti-fouling applications

Fouling, the accumulation and adhesion of unwanted contaminants, is a serious issue around the world in many aspects including industrial transport, marine ecological environment, maintenance of infrastructures, etc. which costs hundreds of millions of dollars and lots of manpower and material resources. Multiscale hierarchical surface structures of superhydrophobic surfaces possess various intriguing properties which provides new platforms for fabricating artificial anti-fouling surfaces. In particular, lotus leaf and shark skin with their unique micro-, nano-, hierarchical surfaces structures are highlighted as emerging tools for anti-bacterial, anti-dust, anti-corrosion, anti-icing, drag reduction applications and so on. In this review, we first provide basic information on two famous superhydrophobic states. After that we outlined the biological models and applications of lotus leaf and shark skin respectively. The self-cleaning effect of superhydrophobic lotus leaf due to their multiscale hierarchical surface structures is discussed after which anti-bacterial applications with three kinds of mechanisms and self-cleaning properties are outlined. Biological models of superhydrophobic shark skin are presented followed by their real-life applications in aircrafts and turbine blades. In addition, we discuss the potential drawbacks of recent biomimetic anti-fouling superhydrophobic surfaces like the loss of anti-fouling hydrophobic materials, adaptability to extreme environments, production and use costs and other problems as well as the possibilities of combine superhydrophobic structures and materials with high temperature resistance, oxidation resistance and other characteristics in order to be applied in more industries fields.

Industrial and biomedical applications of slippery liquid-infused porous surfaces

Abstract Slippery liquid-infused porous surfaces (SLIPS) are biomimetic interface materials that consist of a porous structure or polymer network substrate with a high specific surface area and a perfused liquid lubricant. This surface has an extremely low coefficient of friction and a high degree of antifouling property, which can effectively repel various liquids, oils, ice, biofilms, etc. The tunable performance of SLIPS endows it with promising application prospects in various fields, thus emphasizing the importance of designing diverse SLIPS materials tailored to specific application scenarios in the future. However, owing to the inherent fluid properties of lubricating oil, the surface may encounter challenges associated with lubricant depletion during practical utilization. This review paper focuses on elucidating the principles, design strategies, and fabrication techniques employed for developing SLIPS materials in anti-ice applications, drag reduction applications, and biomedicine. Furthermore, a comprehensive summary of challenges encountered by SLIPS in different domains is provided along with potential avenues for future research to improve the stability and durability of SLIPS. In conclusion, SLIPS shows significant potential for diverse applications, yet necessitates comprehensive research to address its inherent challenges and extend its versatility and functionality across various domains.

Bubble Growth on Hydrophobic Rough Surfaces in the Shear Flow.

It is well known that bubbles will form on a hydrophobic rough surface immersed in water, which can create a surface covered with bubbles and leads to drag reduction. However, it is still not clear how bubbles grow on the surface under flow conditions. In this work, a rotating flow field is created using a parallel-plate setup of a rotational rheometer, and sample surfaces with different roughnesses and wettabilities are examined with different shear rates. The growth of bubbles is exclusively observed on the hydrophobic rough surface, and subsequent drag reduction is also detected simultaneously. The growth of bubbles is attributed to heterogeneous nucleation in the crevices under a local pressure reduction generated by the shear flow. A geometric model is established to describe the profile evolution of the trapped bubble in the crevice based on the contact angle and the pressure balance across the gas-liquid interface, which involves the variations of the Laplace pressure resulting from changes in the local liquid pressure. The growth of bubbles on the hydrophobic rough surface does not need a large decrease of the surrounding pressure or a high moving speed, which will have potential applications in drag reduction under the condition of a moderate shear rate.

Micellar aggregation of poly(acrylamide-co-styrene): Towards ‘self-removing’ polymers from solution

Polymer drag reducing agents (DRAs) are used in hydraulic fracturing processes to reduce frictional drag developed in fully turbulent pipe-flows. The drag reduction lowers energy consumption required to pump fluids. Removal and/or recovery of DRAs from the fracking fluids remains challenging causing environmental issues. We used model aqueous hydraulic fracturing fluids containing poly(acrylamide-co-styrene) P(AAm-co-St) as DRA and demonstrate an approach to ‘self-remove’/recover the P(AAm-co-St) copolymers by up to 55%. This approach involves foaming of P(AAm-co-St) solutions by sparging gas into fluid (at application relevant conditions) resulting in copolymer enrichment in a generated foam phase and subsequent removal from solution. Our observations suggest a simple method to remove or recover DRAs after drag reduction applications from fracking fluids. Liquid foams containing the P(AAm-co-St) copolymer were dried and redissolved in water offering the potential to be reused for further drag reduction applications or, in case of waste, explored for other applications as emulsifier or in macroporous materials.

3D hot laser shock peening without coating based on Leidenfrost effect enables self-armored hydrophobic surface with enhanced fatigue properties

Hydrophobic metal surfaces have widespread applications in self-cleaning, ice removal, corrosion resistance, and drag reduction. The fine structure of these surfaces is crucial for their hydrophobic properties. Currently, pulse laser direct surface texturing is commonly employed to create hydrophobic surfaces, but this method primarily operates at room temperature. However, the rapid cooling rate and significant temperature gradient of the thin melted layer generated at room temperature often result in high stress concentration and cracks within the fine structure, compromising the overall integrity of the hydrophobic surface when subjected to complex external loads. To assess structural robustness by evaluating crack propagation, fatigue performance serves as a vital indicator. The thermal effect helps mitigate thermal cracking caused by direct laser irradiation and introduces an additional strengthening mechanism through dynamic strain aging. By utilizing the Leidenfrost effect, water can act as a confinement layer to achieve high temperature laser shock, which is expected to enhance the fatigue performance of hydrophobic structures. In this study, we propose a technique called 3D hot laser shock peening without coating (3HLSPwoC) as a cost-effective and efficient method to fabricate multi-scale self-armored hydrophobic surfaces with enhanced fatigue properties. We systematically discuss and analyze the wettability and mechanical properties of samples manufactured using different approaches. Furthermore, we reveal the underlying mechanism responsible for the fatigue performance improvement achieved through the 3HLSPwoC process, supported by molecular dynamics calculations and finite element simulations. Compared with the samples manufactured at room temperature, the surface of 3HLSPwoC samples exhibit greater plastic deformation, with no visible cracks on the surface. Additionally, these samples possess higher compressive residual stress and hardness. Notably, 3HLSPwoC samples demonstrate superior fatigue performance and enhanced durability of the hydrophobic properties. 3HLSPwoC has proved to be a novel process for manufacturing advanced hydrophobic surfaces with comprehensive mechanical properties.

Eco-friendly intrinsic self-healing superhydrophobic polyurea/TiO2 composite coatings for underwater drag reduction and antifouling

With more and more exploration of the marine environment, a series of underwater monitoring equipment such as underwater vehicles are used more widely. Reducing the operation cost of underwater equipment and improving work efficiency have become the focus of attention. Superhydrophobic coatings have excellent applications in drag reduction, antifouling and other fields due to their unique surface wettability. This paper reports a superhydrophobic polyurea/TiO2 composite coating with rapid self-healing ability by simple sprinkling or spraying of modified TiO2 nanoparticles on the brushed polyurea coating. The modified TiO2 nanoparticles were driven to migrate to the surface of the coating by the synergistic self-healing effect of the disulfide and hydrogen bonds inside the polyurea, contributing to restoring the superhydrophobicity. This superhydrophobic polyurea/TiO2 composite coating possesses ~11.28 % drag reduction efficiency after being applied to underwater navigation, and it shows ~11.04 times higher water loading capacity than its weight. Moreover, this coating possesses excellent antifouling properties and chemical durability. This work provides new clues for future applications of drag reduction and pollution prevention of underwater exploration equipment.

Synthesis of superhydrophobic FAS-EP/PTFE coating with excellent drag reduction performance and mechanical robustness

Superhydrophobic (SHP) materials have great potential for applications in self-cleaning, anti-fouling, anti-corrosion and drag reduction, but their poor mechanical robustness is a fundamental problem that hinders their practical application. In this work, we successfully and rapidly prepared SHP coating with good durability and drag reduction properties by a simple drop-coating technique after chemical modification and physical mixing. We investigated the effects of modification with 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (FAS-17), a low surface free energy material, and the filling content of Poly tetra fluoroethylene (PTFE) on the hydrophobic property of the as-prepared coating. The maximum water contact angle (WCA) and the minimum sliding angle (SA) of the coating were 160.2 ± 0.4° and 5°, respectively. The coating maintained superhydrophobicity after 4.4 m of abrasion with 400 grit sandpaper and 3 h of water impact, indicating its excellent mechanical durability. In addition, it has outstanding self-cleaning and self-repairing properties. Moreover, the coating was innovatively applied to the surface of the chute, because it remarkably reduced the adhesion between the wet foam block and the chute. These findings here provide a novel insight into the design of a robust SHP coating and suggest a new potential application in express sorting industry for drag reduction.

Drag reduction and optimization on a sphere with the effect of Lorentz force

The flow of a weakly conductive fluid (i.e. seawater) can be controlled by Lorentz force, which holds promising applications in drag reduction. In this paper, the drag reduction on a stationary sphere in the weakly conductive fluid with the Lorentz force on the sphere surface are numerically investigated at Re = 300. The relations among the vortex structures, the hydrodynamic forces, and the effects of drag reduction are discussed before and after the application of the Lorentz force. The results indicate that the fluid near the surface of the sphere is accelerated with the application of Lorentz force. Therefore, the flow separation on the rear surface of the sphere is suppressed, and the periodic shedding mode of hairpin vortices is replaced by the steady double-thread wake structure. Meanwhile, the increase of momentum near the sphere improves the capability to overcome the adverse pressure gradient. Therefore, the pressure on the leeward side of the sphere increases, and then the effect of drag reduction is achieved. Moreover, the effects of drag reduction are distinct with the different locations (θm) of the applied Lorentz force, which reaches the maximum drag reduction rate together with the maximum drag reduction efficiency for θm = 90°.

Laminar drag reduction in surfactant-contaminated superhydrophobic channels

Although superhydrophobic surfaces (SHSs) show promise for drag reduction applications, their performance can be compromised by traces of surfactant, which generate Marangoni stresses that increase drag. This question is addressed for soluble surfactant in a three-dimensional laminar channel flow, with periodic SHSs made of long finite-length longitudinal grooves located on both walls. We assume that bulk diffusion is sufficiently strong for cross-channel concentration gradients to be small. Exploiting long-wave theory and accounting for the difference between the rapid transverse and slower longitudinal Marangoni flows, we derive a one-dimensional model for surfactant transport from the full three-dimensional transport equations. Our one-dimensional model allows us to predict the drag reduction and surfactant distribution across the parameter space. The system exhibits multiple regimes, involving competition between Marangoni effects, bulk and interfacial diffusion, bulk and interfacial advection, shear dispersion and surfactant exchange between the bulk and the interface. We map out asymptotic regions in the high-dimensional parameter space, and derive explicit closed-form approximations of the drag reduction, without any fitting or empirical parameters. The physics underpinning the drag reduction effect and the negative effect of surfactant is discussed through analysis of the velocity field and surfactant concentrations, which show both uniform and non-uniform stress distributions. Our theoretical predictions of the drag reduction compare well with results from the literature solving numerically the full three-dimensional transport problem. Our atlas of maps provides a comprehensive analytical guide for designing surfactant-contaminated channels with SHSs, to maximise the drag reduction in applications.

Sustainable Drag Reduction of Fatty Acid Amide‐Based Oleogel Surface Under High‐Speed Shear Flows

AbstractNepenthes alata‐inspired micro/nano‐textured lubricant‐infused surface (LIS) has shown strong potential in the fields of drag reduction (DR), anti‐biofouling, and self‐cleaning. However, its surface‐slippery property is largely degraded under turbulent shear flow conditions due to the loss of the impregnated oil. This condition inhibits its practical applications to marine vehicles. The mucus‐impregnated tissue systems of marine creatures are primarily based on fatty acid amides (FAAs), such as erucamide or oleamide, which have been commercially utilized as solid‐slip additives. A stable lubricant interface of erucamide‐PDMS composite (EPC) oleogel is formed by cross‐linking erucamide with PDMS gel network prior to infusion of silicon oil. In this study, the surface stability and lubricant retention of EPC are investigated in consideration of DR applications. The fabricated EPC‐oleogel surface exhibits shear stable DR under harsh conditions, such as high pressure, temperature, and shear flow conditions. The surface shows a shear stable DR performance of about 14% even up to a high‐speed flow of 12 ms−1, corresponding to friction Reynolds number (Reτ) of approximately 5000. The superior lubrication stability of FAA‐oleogel at the flow conditions of cruising ships ensures its strong potential for sustainable fuel economy of marine vehicles.

Acoustic responses of underwater superhydrophobic surfaces subjected to an intense pulse

Underwater stability of an air layer trapped in a micro-structure, plastron, is critical in drag reduction applications. Here, we investigate the wetting state and plastron stability of underwater superhydrophobic surfaces (SHS) under an intense acoustic drive. Flat surfaces and SHS are subjected to short acoustic pulses of different intensities. At low amplitude, the comparison between the results of various surfaces shows that plastron behaves like a water–air interface, whose presence can be detected from the phase of the reflected acoustic waves. At moderate intensity, a wetting transition towards a completely wetting state is observed and shown to be triggered by a sufficiently large acoustic radiation pressure. This wetting transition is well captured by a simplified model by balancing radiation pressure with the critical capillary pressure for the interface sliding. Cavitation clouds appear under strong excitation; their sizes and positions greatly depend on the surface acoustic boundary condition. For SHS in a Cassie–Baxter state (with an air layer), cavitation clouds appear at specific locations (from the solid surface) corresponding to the pressure anti-node of the transient standing wave generated by the reflection. This study unprecedentedly demonstrates the capability of acoustic waves to monitor and characterize plastron stability with low and moderate amplitudes, respectively.

Study on the drag reduction performance of high-temperature exhaust pipe by spray cooling

The drag of the exhaust pipe greatly influences the engine power performance of an engineering vehicle. The engine power performance would decrease significantly when the exhaust drag is large. The drag reduction effect achieved by the existing drag reduction is relatively weak; thus, based on spray cooling, drag reduction technology is introduced to solve this problem. The present study aims to determine the influence of spray parameters on drag reduction using an electric heating test bench and to clarify why spray significantly reduces drag using numerical simulations based on Discrete Phase Modeling (DPM). The obtained results prove that increasing the flow value in the test spray flow range of 12–24 ml/s can significantly improve the drag reduction performance. When the spray inclination increases from 45° to 90°, the drag reduction remains, in the beginning, unchanged and then decreases. Under the synergistic effect of the frictional resistance reduction and the dynamic pressure reduction, the resistance downstream of the spray location is significantly reduced. Compared with the existing drag reduction, the spray drag reduction has obtained the ultimate drag reduction effect, and the drag reduction rate is as high as 90 %. To conclude, this research will help promote the application of spray drag reduction to engineering vehicles.

Effects of the Yaw Angle on Air Drag Reduction for Various Riblet Surfaces.

Biomimetic riblet surfaces, such as blade, wavy, sinusoidal, and herringbone riblet surfaces, have widespread applications for drag reduction in the energy, transportation, and biomedicine industries. The drag reduction ability of a blade riblet surface is sensitive to the yaw angle, which is the angle between the design direction of the riblet surface and the average flow direction. In practical applications, the average flow direction is often misaligned with the design direction of riblet surfaces with different morphologies and arrangements. However, previous studies have not reported on the drag reduction characteristics and regularities related to the yaw angle for surfaces with complex riblet microstructures. For the first time, we systematically investigated the aerodynamic drag reduction characteristics of blade, wavy, sinusoidal, and herringbone riblet surfaces affected by different yaw angles. A precisely adjustable yaw angle measurement method was proposed based on a closed air channel. Our results revealed the aerodynamic behavior regularities of various riblet surfaces as affected by yaw angles and Reynolds numbers. Riblet surfaces with optimal air drag reduction were obtained in yaw angles ranging from 0 to 60° and Reynolds numbers ranging from 4000 to 7000. To evaluate the effects of the yaw angle, we proposed a criterion based on the actual spanwise spacing (d+) of microstructure surfaces with the same phase in a near-wall airflow field. Finally, we established conceptual models of aerodynamic behaviors for different riblet surfaces in response to changes in the airflow direction. Our research lays a foundation for practical various riblet surface applications influenced by yaw angles to reduce air drag.

Aqueous Solutions of Associating Poly(acrylamide-co-styrene): A Path to Improve Drag Reduction?

Hydrophobically modified associating polymers could be effective drag-reducing agents containing weak "links" which after degradation can reform, protecting the polymer backbone from fast scission. Previous studies using hydrophobically modified polymers in drag reduction applications used polymers with M w ≥ 1000 kg/mol. Homopolymers of this high M w already show significant drag reduction (DR), and the contribution of macromolecular associations on DR remained unclear. We synthesized associating poly(acrylamide-co-styrene) copolymers with M w ≤ 1000 kg/mol and various hydrophobic moiety content. Their DR effectiveness in turbulent flow was studied using a pilot-scale pipe flow facility and a rotating "disc" apparatus. We show that hydrophobically modified copolymers with M w ≈ 1000 kg/mol increase DR in pipe flow by a factor of ∼2 compared to the unmodified polyacrylamide of similar M w albeit at low DR level. Moreover, we discuss challenges encountered when using hydrophobically modified polymers synthesized via micellar polymerization.

Electrostatic-modulated interfacial crosslinking and waterborne emulsion coating toward waterproof, breathable, and antifouling fibrous membranes

Developing hydrophobic surfaces for flexible fibrous membranes has attracted tremendous attention for their potential applications in waterproofing, antifouling, and drag reduction. However, conventional methods, such as hydrothermal, coating, and phase separation, often involve complex preparation processes,plugging of porous structures,and heavy use of organic solvents. Herein, a facile and eco-friendly assembly strategy is proposed for fabricating superior hydrophobic surfaces on fibrous membranes. Firstly, a hierarchical rough structure was created on the fiber surface using titanium dioxide nanoparticles as building blocks by a one-pot procedure based on electrostatic complexation and interfacial crosslinking. The procedure is performed in aqueousmedia, at low temperature (50℃) and very fast (∼20 min). Subsequently, a waterborne emulsion was developed by low-surface-energy organosilicon self-assembly in aqueousmedia, which was adopted to coat fiber substrate for surface hydrophobization. The amount of organosilicon is reduced by >90 % of that required in the traditional coating. Consequently, the resultant fibrous membranes exhibit a robust hydrophobic surface with UV-resistant,washdurability, photocatalytic self-cleaning effect, and excellent breathable properties. Besides, this general waterborne hydrophobic coating strategy could be applied to various hydrophilic substrates, including fabrics, aerogels, and sponges. This work provides a novel method to design and fabricate multi-functional hydrophobic surfaces.

Robust superhydrophobic composite fabricated by a dual-sized particle design

Superhydrophobic surfaces have shown great potential in various areas such as self-cleaning, anti-icing, drag reduction and biomedical applications. However, it is still challenging to prepare robust superhydrophobic surfaces for real applications. Here, a facile, low-cost dual-sized particle strategy is proposed to fabricate the robust superhydrophobic composite with an “armoured” micro-/nanostructure. As a proof-of-concept, the intrinsically hard quartz sand microparticles (QS MPs) and the epoxy (EP) adhesive are adopted to construct a firm surface frame (EP@QS) as an “armour” to provide mechanical durability while modified superhydrophobic SiO2 nanoparticles (msSiO2 NPs) are confined within the cavities among the QS MPs, forming a nanostructure to impart liquid repellency. Benefitting from the strong “armour”, the EP@QS@msSiO2 composite can reserve excellent water repellency after different kinds of environmental test such as cycled mechanical abrasion, ultraviolet radiation treatment, outdoor exposure damage, tape-stripping test, acid-base treatment and NaCl salt solution immersion, temperature treatment and knife scratching. Furthermore, the substrate versatility and nanoparticle versatility of our strategy are explored and verified. By virtue of the structural advantages, these EP@QS@msSiO2 composite manifest superior self-cleaning property and efficiently directional oil adsorption ability even after mechanochemical damage. Together with robustness and universality, the design strategy of the robust superhydrophobic composite is expected to extend the application scope in harsh nautical applications.

Judicious Design and Rapid Manufacturing of a Flexible, Mechanically Resistant Liquid-Like Coating with Strong Bonding and Antifouling Abilities.

Fluorine-free liquid-repellent coatings have been highly demanded for a variety of applications. However, rapid formation of coatings possessing outstanding oil repellency and strong bonding ability as well as good mechanical strength (e.g., bendability, impact resistance, and scratch resistance) remains a grand challenge. Herein, a robust strategy to rapidly create fluorine-free oil-repellent coatings in only 30 s via rational design of a semi-interpenetrating polymer network structure is reported. The resulting coating manifests strong bonding capability both in air and underwater. More importantly, it not only provides unprecedented oil repellency, even to high-viscosity crude oil, but also achieves both excellent bendability and hardness. This simple yet effective design strategy opens up a new avenue to manufacture multifunctional materials and devices with desirable features and structural complexities for applications in sustainable antifouling, drag reduction, nondestructive transportation, liquid collection, and biomedicine, among other areas.

Ultrafast Self-Healing Superhydrophobic Surface for Underwater Drag Reduction.

The self-healing superhydrophobic surfaces have attracted great interest owing to restoring superhydrophobicity without preparation crafts. However, the self-healing superhydrophobic surface still faces the dilemma of long repairing time. Especially in aqueous environments, superhydrophobic surfaces are highly susceptible to contamination and damage. In the current study, a superhydrophobic surface with ultrafast repairability was developed, which apply for drag reduction in aqueous medium. The prepared superhydrophobic surface can recover superhydrophobicity in only 30 s after severe physical and chemical damage. In addition, this research pioneered the combination of superhydrophobicity and porous structures for underwater drag reduction. The study of drag reduction confirms that the superhydrophobic surface can reduce the frictional drag by about 43% in the water. However, the drag reduction rate of the superhydrophobic surface with the porous structure can be improved to 76% due to increased stability of the air layer. More importantly, the porous structure with the average pore size of 50 μm has the most excellent stability through further experiments on the underwater air layer. This is attributed to the proper size of the pore to effectively balance the capillary force and resist wetting in the marginal region. This study will bring inspiration for the large-scale application of superhydrophobic surfaces and long-term drag reduction.

Optimization of coating parameters for fabrication of robust superhydrophobic (SHP) aluminum and evaluation of corrosion performance in aggressive medium

The huge interest in superhydrophobic surfaces originates from their potential engineering applications in corrosion protection, antifouling, oil recovery, self-cleaning, anti-adhesion, anti-icing, medical dressing, drag reduction and radiative cooling. Despite the progress made in developing superhydrophobic (SHP) coatings, a key challenge is the ability to fabricate mechanically robust SHP surfaces and a proper understanding of the corrosion performance of SHP surfaces in aggressive conditions. Here, we report a simple, rapid, inexpensive, scalable and eco-friendly method for fabrication of mechanically durable superhydrophobic (SHP) aluminum surfaces with self-cleaning properties using a scalable dip-coating method. The coating parameters were optimized to obtain a robust coating with desirable properties such as water contact angle (WCA), sliding angle, self-cleaning, abrasion and corrosion resistance. To obtain good adhesion between the substrate and the coating, chemical etching and hydroxylation of the Al surface were used. At an optimal withdrawal speed of the substrate in the precursor solutions, a maximum WCA of 172.3° ± 1.1° (SA ~ 1° ± 1°) was achieved. The hierarchical micro-nano roughness and the presence of the Si-(CH3)3 group were responsible for the superhydrophobic behavior. The existence of a covalent bond between the Al surface and the middle connecting layer and –O-Si-CH3 groups on the surface of the SHP Al are confirmed by LRS and XPS, respectively. The electrochemical studies in 3.5 wt% NaCl solution show that the Rct value of SHP Al during the initial state was ~2 orders higher than that of the bare sample. The Cdl value of SHP Al was 6 orders less than that of bare after 1 h of exposure in chloride solution. On the SHP surface, a droplet with an impinging velocity of 0.36 m/s showed approximately 7 bounces. The superhydrophobicity of the SHP sample was preserved up to 150 cm abrasion distance. The hierarchical surface morphology and superhydrophobicity (WCA ~151°) were retained by the SHP samples even after 120 h of immersion in 3.5 wt% NaCl, which indicates its suitability in seawater applications such as ships, underwater instruments and pipelines and marine structures. Further, our work provides a framework to develop mechanically robust SHP coating for various applications.